This invention relates to an alarm and more particularly, to a maintenance alarm actuator for signalling the need for cleaning a fluid filter.
In the use of an air compressor or similar compressed air equipment, an air filter may be used to trap contaminant contained in the air lines. In a hydraulic system, a similar filter may be used. Since trapped contaminant blocks fluid flow and causes a drop in line pressure downstream from the filter, periodic cleaning of the filter is necessary for proper operation of the equipment. However, such cleaning is often overlooked or neglected because of a lack of outward indication that a filter should be cleaned.
In the past, a variety of devices have been developed for signalling that a fluid filter needs cleaning. Among such devices are those disclosed in U.S. Pat. Nos. 3,250,242 entitled: "Clogged Filter Indicator Device"; 3,279,418 entitled: "Device for Signalling Need for Cleaning or Replacing Suction Cleaner Dust Bag"; 3,325,010 entitled: "Filter Clogging Indicator"; 3,411,477 entitled: "Pressure Differential Indicator"; and No. Re. 28,268 entitled: "Device for Signalling Need for Cleaning or Replacing Suction Cleaner Dust Bag." Each of the devices disclosed in these patents is a useful device. However, there has remained a need for a device which actuates rapidly and creates a signal which is at full strength immediately, which is balanced for actuation by the same pressure difference regardless of line pressure, which can be reset for later acutation without shutting off the fluid line with which it is connected and which is itself free from clogging by contaminant trapped in the filter.